Estimating Sums And Differences


When estimating sums and differances remember for estimating there is no correct answer.
Estimate means to find an approximate value, but you have to be reasonable about it.

Example:

Rond to the Nearest 10
32.9 ~ 30.0
56.4 ~ +60.0 ~ = Round to
answer: 90.0

Round each decimal term that will be subtracted.
Subtract the rounded terms

Example: Estimate the difference of 0.988 - 0.53
Round 0.988 - 0.53 to 1 - 0.5
Subtract the rounded numbers to obtain the estimated difference of 0.5
The actual difference of 0.988 - 0.53 is 0.458

Some uses of rounding are:


Checking to see if you have enough money to buy whatever it is that you want to buy.
Getting a rough idea of the correct answer to a problem


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